What was the actually reason for stopping production of the D1 at those days ?

According to the non-availability PCM63 from Burr Brown also the D1 was shortly later no longer available. I have read anywhere, that the follow successors PCM1702, PCM1704, PCM1792 and PCM1794 unfortunately haven't the same musical character despite better measuring results and for this reason the production of the D1 was not continued.

The D1 started out as a project for my own use. Nelson had a nice analog circuit and it kind of grew from there. I would say it's timing was off coming late to the game as CD players became better. Parts became an issue like the PCM63. I still use the 63 in mine. The guys who designed both the 63 and 1704 preferred the 63 for some internal clocking issues if I remember correctly. It just sound pretty good.

Now we see a return to the external USB DAC these days. Maybe time to play again with digital.

The D1 started out as a project for my own use. Nelson had a nice analog circuit and it kind of grew from there. I would say it's timing was off coming late to the game as CD players became better. Parts became an issue like the PCM63. I still use the 63 in mine. The guys who designed both the 63 and 1704 preferred the 63 for some internal clocking issues if I remember correctly. It just sound pretty good.
Now we see a return to the external USB DAC these days. Maybe time to play again with digital.

Both according varios (a lot of) comments here on this forum and my own experience the I/U (I/V) converter has a very great influence of the individual sonic character (together with the kind of digital filtering and the kind of reclocking).
Can we assume, that in this comparison at least the I/U converter for the PCM1704 was also optimally dimensioned (in the same basicly manner than by the PCM63)?
Or is it also possible that this was not the case and a not so good suited I/U converter was the real reason for this audible sound impression?